class Compiler{
    constructor(vm){
        this.el = vm.$el
        this.vm = vm
        this.compile(this.el)
    }

    compile(el){
        let childNodes = el.childNodes
        Array.from(childNodes).forEach(node =>{
            if(this.isTexNode(node)){
                this.compileText(node)
            }else if(this.isElementNode(node)){
                this.compileElement(node)
            }
            if(node.childNodes && node.childNodes.length){
                this.compile(node)
            }
        })
    }
    compileElement(node){
        Array.from(node.attributes).forEach(attr =>{
            let attrName = attr.name
            if(this.isDirective(attrName)){
                attrName = attrName.substr(2)
                let key = attr.value
                this.update(node,key,attrName)
            }
        })
    }
    update(node,key,attrName){
        let atrName = attrName.split(':')
        let updateFn = this[atrName[0]+'Updater']
        if (atrName.length > 1){
            updateFn && updateFn.call(this,node,atrName[1],key) 
        }else{
            updateFn && updateFn.call(this,node,this.vm[key],key) 
        }
        
    }

    textUpdater(node,value,key){
        node.textContent = value
        new Watcher(this.vm,key,(newValue)=>{
            node.textContent = newValue
        })
    }
    modelUpdater (node,value,key){
        node.value = value
        new Watcher(this.vm,key,(newValue)=>{
            node.value = newValue
        })
        node.addEventListener('input', () => {
            this.vm[key] = node.value
        })
    }
    onUpdater(node,value,key){
        node.addEventListener(value, this.vm.$options.methods[key])
    }
    htmlUpdater(node,value,key){
        node.innerHTML = value
        new Watcher(this.vm, key, (newVal) => {
            node.innerHTML = newVal
        })
        // document.write(value)
    }
    compileText(node){
        let reg = /\{\{(.+?)\}\}/
        let value = node.textContent
        if(reg.test(value)){
            let key = RegExp.$1.trim()
            node.textContent = value.replace(reg,this.vm[key])

            new Watcher(this.vm,key,(newValue)=>{
                node.textContent = newValue
            })
        }
    }
    isDirective(attrName){
        return attrName.startsWith('v-')
    }
    isTexNode(node){
        return node.nodeType === 3
    }
    isElementNode (node) {
        return node.nodeType === 1
    }
}